Constant speed drive and generator

ABSTRACT

An integrated constant speed drive and generator for providing electrical power to aircraft including a constant speed drive housing open at one end and having drive components therein including a differential and an hydraulic drive, and a generator housing also open at one end and having a generator mounted therein with the housings interconnected so that they open to one another and define a common sump for generator cooling fluid as well as drive control and lubrication fluid, there being provided a single charge pump in the generator drive housing portion that provides hydraulic fluid for controlling the drive, lubricating the drive components, and cooling the generator rotor and stator by direct contact of the cooling fluid therewith.

it States Patent 3,274,855 9/1966 Reynoldsetal.

ABSTRACT: An integrated constant speed drive and generator for providingelectrical power to aircraft including a constant speed drive housingopen at one end and having drive components therein including adifferential and an hydraulic drive, and a generator housing also openat one end and having a generator mounted therein with the housingsinterconnected so that they open to one another and define a common sumpfor generator cooling fluid as well as drive control and lubricationfluid, there being provided a single charge pump in the generator drivehousing portion that provides hydraulic fluid for controlling the drive,lubricating the drive components, and cooling the generator rotor andstator by direct contact of the cooling fluid therewith.

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PATENTEDAPRNIQH V 3576143 sum 8 [1F 8 CONSTANT SF 1) AND GENERATORBACKGROUND OF THE PRESENT INVENTION There have been provided in the pastaircraft-enginemounted constant-speed drives for the purpose ofmaintaining a constant-output shaft speed with variations in enginespeed, for example from 4500 rpm. to 9000 r.p.m. Such a drive is shownin the U.S. Pat. of C. .l. Gantzer, No. 3,365,981, assigned to theassimtee of the present invention. Driven by these drives are generatorsin the 30 to I50 kv.-a, range which provide, for example,400-cycle-per-second electricity for operation of aircraft equipment andaccessories.

These two units, that is, the constant speed drive unit and thegenerator unit, have in the past usually been constructed as completelyindependent units by different manufacturers, fastened together for thepurpose of mounting and driving only.

The constant speed drive units generally include a gear differentialdriven by the engine, positive displacement hydraulic pump and motorunits for controlling the speed ratio of the differential gearing, andgovemor-operated control circuits for varying the displacement of thehydraulic units to achieve a constant speed output, as well as scavenge,lubrication and charge fluid circuits for these components. The constantspeed drive housings have been sealed housings separate from thegenerator housing.

The generators commonly interconnected with these constant speed driveshave also included independent sealed housings with stator and rotorcompletely supported and mounted therein. An independent lubricationcircuit for bearings, seals, and splines has been provided whennecessary. The rotor and stator are conventionally cooled by air.

It has been found desirable for the constant speed drives and generatorsto be improved by providing units of smaller size, lower weight andhigher reliability. The constant speed drives themselves have asignificantly higher reliability, Le. the m.t.b.f. (mean time betweenfailure) is far longer on the constant speed drives than on thegenerators themselves, and this divergence prompted the search which ledto the design of the present integration of the constant speed drive andgenerator into a substantially common housing.

SUMMARY OF THE PRESENT INVENTION In accordance with the presentinvention an improved constant speed drive and generator has beenprovided through the integration of the constant speed drive andgenerator into a common housing. While the drive housing may bephysically separated in the sense that it is a separate part from thegenerator housing, the two housings freely communicate with one anotherand thus provide essentially one housing. Both housings are designed andcommunicate in such a way as to provide a common sump for the constantspeed drive components as well as the generator components.

A charge pump is provided which draws cool fluid from a reservoir formedintegrally within the constant speed drive portion of the housing tosupply control fluid to the displacement and governing control circuitfor controlling output shaft speed as well as providing lubrication forthe differential gearing. In the present integrated drive, however, thecharge pump also serves to provide cooling fluid, through suitablepassages integrally formed in the housings, directly in contact with thegenerator stator for the purpose of cooling the generator.

The charge pump also supplies cooling fluid through a suitable passage.coaxial with the rotor for direct contact cooling of the rotor itself.

There are several advantages to this arrangement over the prior constantspeed drive and separate generator units. Firstly, the sealed wallbetween the constant speed drive and generator has been eliminated aswell as the necessity of rotating contact-type seals at the mating endsof the generator and constant speed drives presently in use. Anadditional benefit to the generator is that a common environment isprovided with the drive components which is more favorable than beingopen to the atmosphere as in prior air-cooled generators. The splinelife in the generator is also increased due to its being continuouslylubricated by fluid from the single charge pump located in the drivehousing. If desired, a single set of pumps can be provided for thescavenge, charge, cooling and lubrication functions for both drive andgenerator which may be more conveniently located in the constant speeddrive portion of the housing resulting in space and weight savings sincethey are more easily driven from this location and their number isreduced.

A further feature of the present invention is that one of thedifferential elements is in line and directly connected with thegenerator rotor and rotates at the same speed therewith eliminating theneed for intermeshing gears between the differential and the generator.An ancillary feature to this is that the entire differential is alignedwith the generator axis as well as the input shaft so that additionalgearing between the input shaft and the differential is eliminated.

A still further feature of the present invention is in the provision of,in one embodiment, two hydraulic drives in parallel controlled by asingle governor which reduces the maximum diameter of the integratedconstant speed drive and differential.

Moreover, it is possible for generators to operate at as much as percentof their rated load continuously without damage whereas in conventionalair-cooled generators such overloads can be tolerated only for a fewminutes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of oneembodiment of the present invention;

FIG. 2 is a longitudinal cross section of an integrated drive andgenerator generally similar to the one shown in FIG. 1;

FIG. 3 is a cross section taken generally along line 3-3 of FIG. 2,showing the charge pump and scavenge pump mounting surfaces and ports;

FIG. 4 is a cross section taken generally along line 4-4 of FIG. 2,showing the charge pump and scavenge pump mounted in position along withthe control governor;

FIG. 5 is a fragmentary section taken generally along line 5-5 of FIG.4, showing the charge pump filter;

FIG. 6 is a cross section taken generally along line 6-6 of FIG. 2,showing several of the charge pump passages;

FIG. 7 is a fragmentary section taken generally along line 7-7 of FIG.1;

FIG. 8 is a fragmentary section taken generally along line of FIG. 6;

FIG. 9 is a fragmentary section taken generally along line 9-9 of FIG.41, showing the inlet passage for stator cooling fluid;

FIG. 10 is a fragmentary section talten generally along line 10-10 ofFIG. 4, showing the return passage for stator cooling fluid;

FIG. 11 is a fragmentary section taken generally along line 11-11 ofFIG. 4, showing the stator cooling fluid passages;

FIG. 12 is a fragmentary section taken generally along line 12-12 ofFIG. 11;

FIG. 13 is a fragmentary section taken generally along line 13-13 ofFIG. 4;

FIG. 14 is a fragmentary section showing the generator housing sump;

FIG. 15 is a fragmentary section taken generally along line 15-15 ofFIG. 6, showing the inlet reservoir swirl chamber;

FIG. 16 is a fragmentary section taken generally along line 16-16 inFIG. 4 showing the charge pump;

FIG. 17 is a fragmentary section of the FIG. 4 section;

FIG. 18 is a fragmentary section taken generally along line 10-18 ofFIG. 17 showing the transmission displacement control governor;

FIG. 19 is a fragnentary section taken generally along line 19-19 ofFIG. 17 showing the hydraulic unit displacement control motor;

FIG. 20 is a schematic illustration of another embodiment of the presentinvention;

FIG. 21 is an hydraulic circuit schematic for the integrated constantspeed drive and generator shown in FIG. 20, and;

FIG. 22 is a longitudinal section of the drive portion of the embodimentshown in FIG. 20.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to thedrawings and particularly the embodiment shown in FIG. I, an integratedconstant speed drive and generator is shown with its associatedhydraulic circuit, some parts of which are enclosed within the housingfor the unit and some of which are not as will appear hereinafter. Theintegrated constant speed drive 10 is adapted to be mounted on theengine gear box of the associated aircraft engine with the input shaft12 driven in rotation by the engine through the gear box. It should beunderstood that shaft 12 may vary in speed with the engine and thus, incontemporary aircraft design and gear box configuration, may vary inspeed from zero to 9,000 r.p.m. during normal use. The integrated drivedifferential 10, however, is designed in one actual construction toprovide a constant generator speed, or constant output shaft speed e.g.l2,000 rpm. for input shaft speeds of shaft 12 of between, for example,4,500 to 9,000 r.p.m. which is suflicient to include normal engine speedranges.

The integrated drive and generator 10 is seen to include generally adrive housing 14 with an hydraulic drive 15 therein and a generatorhousing 17 with a generator 18 therein connected to the drive housing 14with a differential 20 mounted partially within each of the housings I4and 17.

Input shaft 12 is coaxial with and drivingly connected to differentialgear carrier 22 which rotatably carries intermeshing pinions 24 and 25.The gear carrier 22 also has a ring 28 mounted for rotation therewithwhich has a gear thereon meshing with gear 30 connected to a variabledisplacement axial piston hydraulic unit 34.

The hydraulic unit 34 is hydraulically interconnected through suitableconduits (not shown in FIG. I) in fixed displacement hydraulic unit 36which is also of the axial piston type. The hydraulic unit 36 isdrivingly connected through gear 38 with a stepped sleeve ring gear 40having internal teeth as at 41 interengaging pinion 24.

The differential 20 also includes another sleeve-type ring gear 48 withinternal teeth 439 thereon intermeshing with pinion and driven therebyin rotation. The above described components define generally what istermed in the art an output differential. With carrier 22 serving as theinput and the sleeve ring gear 48 functioning as the output, thehydraulic drive 15 is suitably varied to control the speed of controlsleeve ring gear 40 to provide a constant output speed of output ringgear 68.

Output ring gear 48 is connected through a suitable overrunning clutch52 to drive generator rotor 54.

The generator rotor 54 is supported at its left end in housing 17 bybearing 56 and at its right end by output sleeve bearings 57 and 58through bearing 72 between the sleeve 48 and an intermediate shaft 73.Intermediate shaft 73 rotates with shaft 54 due to the interconnectingfunction of rotor sleeve 70, which is suitably fixed to both shaft 54and shaft 73.

That is, the output sleeve is supported in housing portion 76, the shaft73 is supported within the output sleeve 48 and the rotor shaft 54 isfixed to rotate with the shaft 73 with the sleeve 70 maintainingalignment therebetween.

In operation, governor 73 which is responsive to the speed of outputsleeve 48, delivers control fluid through passage 80 to a control piston82 which varies the displacement of hydraulic unit 34 to control thespeed ratio between carrier 22 and output 48 to maintain a constantspeed of rotor shaft 54 as input speed of shaft 12 varies thus producinga constant frequency signal from generator 18.

The hydraulic system of the drive and generator 10 shown in FIG. 1 isillustrated in purely schematic form and it should be understood thatall of the components and passages shown are actually within thehousings M and 17 with the exception of scavenge filter 84 and scavengefluid cooler 85.

The lubrication system shown is for the purpose of providing lubricatingfluid to the drive and generator components, control fluid to thecontrol circuit for varying transmission drive ratio and for providingcooling fluid to the generator 18. Toward this end a charge pump88 isprovided which supplies fluid through a charge filter 89 to governor 78through passages 90 and 91. Cooling fluid is provided for the stator 92of generator 18 through passages 94, 95, 96 and 97. For lubricating, thedifferential gearing 20 as well as the generator splines, rotor shaft 54is hollow and communicates with passage 94 so that fluid is deliveredthrough the rotor to lubricate the various gear elements in thedifferential as well as several of the generator parts. Moreover,suitable means, not shown in FIG. 1, may be provided for the purpose ofcooling the rotor 98 with the generator. It should be understood thatthe cooling of the generator rotor and stator is by direct contact withcool hydraulic fluid supplied through passage 94.

Makeup fluid is supplied to the hydraulic drive 15 through passage 98and the excess capacity of charge pump 88 is delivered over chargerelief valve 100 through passage 101 to the inlet of a scavenge or sumppump 104. The scavenge pump draws fluid through passage 106 from acommon sump 108 which communicates with both housings M and 17 so thatsump 108 collects fluid from the components in both housings. Scavengepump 104 delivers fluid through passage 110, through the scavenge filter84 and cooler 85, through passage 112 to a swirl chamber 114 in areservoir 115 which is defined by a suitable partition in the housing 14separating it from the common sump 103. Passage I18 conveys fluid fromthe reservoir tank 115 to the inlet of charge pump 88.

The embodiment of the present invention shown in FIGS. 2 to 19 issubstantially the same as the schematic illustration of FIG. 1 with theexception that the input shaft projects from the generator end of theintegrated housing rather than the constant speed drive end thereof.Viewing initially the longitudinal, sectional view in FIG. 2 a constantspeed drive and generator combination is shown which is seen to includea generally cylindrical generator housing 122 having its left end openand a generally cylindrical drive housing 124 having its right end open.The housing members 122 and 124 are fixed together by suitable fasteners(not shown). An externally splined input shaft 126 is seated in bearing128 and projects centrally from the generator housing 122. The inputshaft 126 like shaft 12 in the FIG. 1 construction, is adapted to bedriven by one of the aircraft engines through a suitable gear box. Theinput shaft drives a gear carrier 130 of gear differential 132 through aquick disconnect coupling 133. The quick disconnect coupling 133 may beactuated by solenoid 136 disconnecting the engine from the drive 120.The construction and the operation of the quick disconnect 133 is shownand described in more detail in the Gantzer US. Pat. No. 3,365,981 andreference should be made thereto for more complete description thereof.

The elongated pinion carrier I30 rotatably receives elongated pinions134 and 135 which intermesh centrally as shown at 138. A steppedsleevelike control ring gear is provided rotatably supported on theelongated gear carrier 130 by bearings 142 and M3. Ring teeth 144 areformed on the right end of sleeve gear 140 integrally therewith andintermeshing with pinion 13 3 on the left end of the gear teeth thereof.The left end of the elongated gear carrier 130 is supported in bearing148 mounted in a bearing frame boss M9 integral with an aperturedsupport and dividing partition 150 formed on the housing member I24.

A stepped output sleeve gear 146 is coaxially disposed with respect tothe input shaft 126 as well as the control sleeve gear 140, androtatively supports the gear carrier 130 by bearing 148' as well asbeing externally supported by bearings 152 and 322 reacting againstgenerator shaft 158.

The entire differential is coaxially aligned with the input shaft 126and is seen to be partially disposed or located within generator rotorshaft 158. Generator 160 is seen to include a stator coil 161 mountedfixedly in housing 122 and a rotatable rotor 162 fixed to shaft 158.There is also provided suitable exciter windings 164 known to beconventional part of AC generators. The right end of hollow rotor shaft158 is rotatably mounted in bearing 168 seated within a suitable boss inthe end portion of housing member 122. The left end of hollow rotorshaft 158 is supported in bearing 170 carried and in turn supported bythe main partition member 150. Thus, it may be seen that the right endof the differential is in effect supported within the hollow generatorrotor shaft 158.

The generator or rotor 162 is driven by direct connection with theoutput sleeve gear 146, which has internal teeth 168 meshing with tlhegear teeth at the right end of pinion 135, through overrunning clutch1711' approximately centrally located in the rotor shaft 158 withrespect to the rotor 162.

In a fashion similar to FIG. 1 construction, by suitably controlling thespeed of control gear 140 with respect to the speed of the input shaft126 and carrier 131), the desired constant output speed of output ringgear 146 and rotor 162 may be achieved.

For the purpose of controlling the speed of sleeve ring gear 140 avariable displacement hydraulic drive 175 is provided including avariable displacement axial piston hydraulic unit 177 and a fixeddisplacement axial piston hydraulic unit 179. For a more completedescription of the details of these hydraulic units reference should bemade to the Gantzer US. Pat. No. 3,365,981 which shows hydraulic unitsof similar construction. Suffice it to state that by pivoting cam 182the displacement of the hydraulic drive 175 may be varied as desired toachieve infinite variations in the relative speeds of shafts 184 and 185drivingly connected respectively to hydraulic units 177 and 179. Theunits 177 and 179 will at times act as pumps and at other times act asmotors or metering devices.

The hydraulic unit 177 is driven by the input shaft 126 through gearcarrier 138 and a hollow shaft 186 splined to the left end of gearcarrier 131) and rotatably supported at its left end by bearing 186 inthe closed end of housing member 124. The shaft 186 has a gear 188integrally formed thereon and intermeshing with gear 189 formedintegrally with hydraulic unit shaft 184. The hydraulic drive 175 issupported in housing member 124 by bearing 188' which supports shaft 184and by bearing 190 which supports shaft 185. Formed integrally withshaft 185 is a gear 192 which intermeshes with an external gear 194formed integrally with control sleeve gear 140 of the differential forthe purpose of controlling the speed and direction of rotation of thecontrol gear.

By suitably controlling the direction and extent of displacement of thecam 182 from its neutral or zero stroke position the control gear 148may be rotated in either direction of rotation at speeds sufficient tomaintain a constant output shaft speed from output sleeve gear 146 andconsequently the rotor 162 which is driven in rotation thereby.

Viewing FIG. 4 a charge pump 2011 is provided for supplying chargecontrol and lubricating fluid to the constant speed drive as well ascooling and lubricating fluid to the generator 160. The charge pump issupported on a mounting plate 201 (FIG. 3) formed integrally withhousing member 124 and extending generally transversely thereto in aplane adjacent the partition 1511. Mounting plate 201 has an arcuateinlet port 204 and an arcuate outlet port 285. It should be understoodthat the charge pump 280 is removed from the view shown in FIG. 3. Thecharge pump 201) supplies fluid under pressure through outlet port 205and a tube 267 (FIG. 5) longitudinally rearwardly in housing 124 asviewed in FIG. 2 to a charge pump filter 211) seated within a boss 212formed within the housing 124 and extending generally radially withrespect thereto as shown in FIG. 6. The charge filter 21 may be removedby removal of fitting 214. After passing through the charge filter 2111charge fluid is supplied to an irregular passage 216 extendingtransversely near the end of housing member 124 and formed integrallywith the housing.

As may be seen in FIG. 18 a governor 218 is provided mounted withinhousing portion 124 and extending longitudinally adjacent the closed endthereof. Governor 218 includes a rotating sleeve 219 and ports fluidselectively to a displacement control 222 shown in FIG. 19. Thedisplacement control 222 controls the position of hydraulic unit cam 182and thus varies the displacement and drive ratio of the fluid drive 175.Governor 218 is driven by the output sleeve gear 146 through gear 224formed on the periphery thereof which interengages the idler gear 226and this gear in turn drives gearing (not shown) which is drivinglyconnected to the rotating sleeve 219 in governor 218 for the purpose ofrotating the same at a speed proportional to the speed of generatorrotor 162.

Viewing FIG. 8 control fluid is supplied from the charge pump to thesleeve 219 through passage 216 extending from the charge filter 210,through passage 225 intersecting and extending perpendicular to passage216. Passage 225 is formed integrally with the end of housing 124 in aplane extending radially through the axis of shaft 186. Charge fluid inpassage 225 communicates with a similar opposed passage 228 across aslotted fitting 230 which serves to retain a feed tube 233 in positionwithin shaft 186. Passage 228 is also formed integrally with the housing124 and communicates with a longitudinally extending tube 231 projectingfrom the end of the housing member 124 and extending toward thegenerator. As seen in FIG. 18 the tube 231 is fitted within a valvehousing 236 which defines a passage 238 communicating with the tube 231for the purpose of supplying control fluid to the sleeve 219.

The governor 218 has a valve (not shown) which shifts axially inresponse to the speed of governor 218 and the speed of sleeve gear 146to selectively port fluid through passage 240 and 241 (FIG. 17) to thedisplacement control 222 and more particularly to chamber 243 (FIG. 19)of the displacement control.

For the purpose of cooling the stator 161 of generator charge fluid inpassage 216 is conveyed to a generally axially extending passage 246(FIGS. 4 and 6) formed integrally in the housing periphery 124. As maybe seen in FIGS. 9 and 11 passage 246 communicates with passage 248extending generally axially in drive housing member 124 and to the openend 249 thereof. Passage 248 also appears in dotted lines in FIG. 4. Thecharge fluid in passage 248, which is in fact cooling fluid for thegenerator stator, passes across the interface of the housing members 124and 122 into passage 251 extending axially in the generator housing 122as may be seen in FIG. 11. Passage 251 communicates through radialpassages 253 in housing member 122 with an arcuate recess 264 (see alsoFIGS. 2 and 12) which extends almost 360 within the housing member 122adjacent and aligned with the stator 161.

Fluid flowing in recess 264 is in direct contact with the stator 161 andcools the stator as it flows around the same and exits through radialpassages 266 as seen in FIG. 12, similar in construction to radialpassages 253. The cooling fluid exits in the opposite direction throughaxially extending passage 267 also formed integrally in housing member122 back toward the interface 242 between the drive and the generatorhousings. As may be seen in FIG. 10 the exiting stator cooling fluidfrom the generator housing 122 enters the drive housing 124 throughpassage 268 and passes rearwardly through the drive housing to a systempressure makeup valve 270 shown in FIG. 7. The valve 270 serves to portfluid to the low pressure side of the hydraulic circuit (not shown)interconnecting the hydraulic units 177 and 179.

The excess hydraulic fluid supplied by the charge pump 2118 for theentire hydraulic circuit is relieved over a charge pressure relief valve272 shown in FIG. 7 through passage 174 extending transversely in drivehousing 124 as may be seen in FIG. 7, to the other side of the drivehousing where it opens as shown at 276 in FIG. 4 into a common sumpwhich collects leakage and excess fluid for both the components in drivehousing 124 and generator housing 122.

It should be understood from viewing FIGS. 3 and 4 that a partition 279is provided in drive housing 124 dividing the drive housing into areservoir or tank 280 hydraulically sealed from a common sump 282 forboth generator and drive housing 122 and 124 respectively. The partition279 extends up to the mounting plate 201 which also defines mountingplate for scavenge pump 283 as shown in FIG. 4. Apertures such as 285and 286' in the mounting plate 201 provide sump communication betweenthe drive housing and the generator housing. It should be understoodthat mounting plate 201, as noted above is formed with the partition 150between the generator and drive housings. As shown in FIG. 3, thescavenge pump 283 has an inlet port 286 communicating with the sump 282freely, and an outlet port 288, both formed in the mounting plate 201.The scavenge pump 283 serves to draw fluid from the common sump in thehousings and to deliver fluid outside the housings through a suitablescavenge filter and cooler (not shown in FIGS. 2 to 19) and to returnfluid to the reservoir 280. As shown in FIG. 14, defined within thegenerator housing 122 is a generator portion 294 of sump 282 that freelycommunicates with the interior of the generator housing and the inlet ofthe scavenge pump 283 through ports 285 and 286 shown in FIG. 4. Thegenerator surnp portion 294 collects excess cooling fluid from thegenerator as well as lubrication fluid leakage from the bearings withinthe generator housing.

The outlet 288 of the scavenge pump 283 delivers fluid to passage 290 asseen in FIG. 3 to a scavenge fluid housing outlet 293 shown in FIG. 13.

Suitable conduits, (not shown in FIGS. 2 to 19) are provided connectedto port 293 to convey the fluid to a cooler and through a scavengefilter such as shown at 84 and 85 in the FIG. 1 construction, and backto an inlet port 295 formed in the end of the drive housing 124 as shownin FIG. 15. Hydraulic fluid entering the port 296 passes through aflared inlet 300 into a conventional swirl chamber 302. From the swirlchamber 302 the filtered and cooled hydraulic fluid flows directly intothe reservoir or tank 280. As seen in FIG. 16 the charge pump 200 has aninlet tube 304 which opens as the at 305 directly into the reservoir 280so that it draws cooled and filtered hydraulic fluid therefrom.

The charge pump 200 also delivers charge fluid for the purpose oflubricating the gearing in the drive as well as for cooling the rotor162 of the generator by direct contact. Toward this end, a portion ofthe charge fluid flowing in passage 225 as shown in FIG. 8 enters feedtube 233 mounted centrally within the drive housing 124 and flowstherefrom through an axial passage 308 in the gear carrier 130 as shownin FIG. 2. A portion of this fluid flows radially outwardly of thecarrier to lubricate the adjacent bearings such as bearings 142, 143 and148.

From passage 308 charge and cooling fluid flows through diagonalpassages 310 into hollow sleeves 312 supporting the differential pinions134 and 135. A portion of this fluid leaks between the carrier and theends of the pinions for the purpose of lubricating the pinions. Afterpassing through the sleeves 312 fluid flows through passages 314 on theother end of the differential pinions and from there into an axialpassage 316 also formed in the carrier.

Radial passages 315 are formed in carrier 130 communicating with axialpassage 316 permitting the outward flow of fluid to within the rotorsleeve 158. This fluid is thrown outwardly by centrifugal force andpasses through passages 320 in the rotor sleeve 153 and from there intodirect contact with the rotor 162. Suitable additional means may beprovided for directing the cooling flow from passages or ports 320 intodirect contact with the rotor 162. Fluid from passages 318 may also beused for lubricating bearing 322 as shown in FIG. 2.

An alternative integrated constant speed drive and generator 400 isshown in FIGS. 20 to 22. This drive and generator combination is similarto that disclosed in FIG. 1, and generally similar to that disclosed inFIGS. 2 to 19 with the primary exception that the differential piniongears are not located partially within the generator rotor sleeve. Thisreduces rotor size somewhat and decreases centrifugal forces on therotor. An additional difference from the FIGS. 2 to 19 construction isthat the cooling fluid for the rotor and the lubricating fluid for thedifferential gearing flows from the generator housing to the drivehousing rather than vice versa.

Viewing FIG. 20 the drive and generator 400 is seen to include agenerator housing 401 enclosing a stationary generator stator 402 and arotatable rotor 403 as well as an exciter assembly 404. The right end ofrotor shaft 405 is supported in a bearing 406 in generator housing 401and the left end of rotor shaft 405 is supported within a splined sleeve410 shown in FIG. 22 which is driven by the output of the constant speeddrive.

Fixed to the generator housing 401 is a drive housing 412 which is shownreversed in FIG. 22 with respect to the view in FIG. 20. The drivehousing 412 supports an input shaft 414, adapted to be connected to theengine, in bearing 416. The input shaft 414 is connected to drive anelongated gear carrier 418 through a quick disconnect coupling 419. Thegear carrier 418 forms part of an elongated differential 421 of similarconstruction to the above described embodiments.

More particularly, differential 421 includes two pinion gears 423 and424 rotatably mounted on sleeves 425 and 426, respectively, in turnmounted in the elongated gear carrier 418. A stepped control ring gear428 has internal ring teeth 429 engaging the teeth on gear 424 and anoutput sleeve ring gear 432 has internal ring gear teeth 433 drivinglyengaging pinion 423. As with the other embodiments by suitablycontrolling the speed and direction of control gear 428 a constantoutput speed may be achieved from the output 432.

The differential is supported in its right end (as viewed in FIG. 22) bybearing 438 mounted on a bearing flange 439 fixed to the right end ofthe drive housing 412. Carrier 418 is supported in the control gear 428by bearings 440 and 441.

The left end of the differential 421 is supported in bearings 442 and443 mounted centrally in the left end of housing 412 as seen in FIG. 22,which support the output sleeve gear 432. The left end of differentialgear carrier 418 is supported in the output ring gear 432 by bearing445. The internally splined generator coupling sleeve 410 is connectedto the output sleeve gear 432 by an overrunning clutch 446 in additionto a bearing 447.

It should be understood that the input shaft 414 and the differential421 are supported with the drive housing. Also supported within thedrive housing are two hydraulic drives 450 (only one shown in thedrawings) similar in construction to the hydraulic drive shown in FIG.2. The provision of two hydraulic drives 450 decreases the requireddiameter of the drive housing 412. Suffice it to state that one end ofeach of the drives as shown in FIG. 22 is connected through gear 451 andgear 452 to the gear carrier 418, while the other end of each of thedrives is connected through gear 454 and gear 455 to the control gear428. By varying the direction and extent of displacement of cam 459 thespeed and direction of control gear 428 can be varied and a constantoutput speed may be achieved from output gear 432.

It should be understood that the input shaft 414 and the differential421 are coaxially disposed with respect to the housing 412 as well asthe housing 401 for the generator in a fashion similar to theembodiments described above even though they appear offset in FIG. 22because of this being an irregular sectional view.

For the purpose of maintaining a constant output speed a controlgovernor 457 (see also FIG. 21) is provided which is driven by theoutput ring gear 432 through gear 459'.

Governor d5? selectively ports fluid to a control motor which varies thedisplacement of cam ass to achieve a constant speed of the generatorrotor 403.

The gear ass, driven by the output, also drives gear Ml integrallyformed with shaft 462 which in turn drives both a scavenge pump and acharge pump 464 both coaxially mounted in the drive housing 412.

In addition to scavenge pump Q63, a generator scavenge pump 467 isprovided in the drive housing 412 for the purpose of scavenging thegenerator housing 401.

The drive housing 412 has a separate reservoir 470 (FIGS. 20 and 21)therein which communicates with the inlet of charge pump 2M forsupplying filtered and cooled fluid thereto.

Charge pump was delivers fluid through a rearwardly and axiallyextending passage M4 in housing 412 to a charge fluid filter Md (FIGS.21 and 22).

From the charge filter fluid flows through passage 472 (FIG. 21) to thehydraulic drives 450 through passage for the purpose of supplying makeupfluid to the working conduits of the hydraulic drive did). Moreover,charge fluid is supplied through line M2 to the governor d5! with theexcess charge fluid being delivered back to a sump 483 within the drivehousing.

For the purpose of cooling the generator and lubricating thedifferential, fluid from line 472 flows through line 486 to nozzles 437and 8 which spray cooling fluid in direct contact with stator dill Fluidin passage 6 also passes down the end of the generator housing and intoa central passage 4190 (FIG.

centrally disposed in the generator rotor shaft 405. Radial passages 492and 493 in the generator rotor 405 serve to spray cooling fluid on therotor 403 of the generator for direct contact cooling thereof.

The remaining fluid in passage 4% passes through the end of the rotorshaft was and into an interfitting tube 4% shown in FIG. 22 seatedwithin the gear carrier dill. This tube has limited leakage to lubricatethe spline and coupling 419 and the remainder passes through the centralpassage therein, through diagonal ports 4% to the interiors of thepinion sleeves 425 and 412%. A portion of the fluid therein leaks out tolubricate the pinion gears and the remaining portion passes throughpassages 501 in the gear carrier M8 on the other side of the pinions.Some of this fluid leaks along splines 5613 and 504 for the purpose oflubricating the same and the remainder passes out radial passages 506 inthe input assembly of shaft 4M into the drive sump M3.

The generator mavenge pump do? conveys fluid through I line 508 to thereservoir 4'70 in housing M2 (shown in FIG.

21). The drive scavenge pump $63 conveys fluid through passage Sill outof the drive housing through a cooler 512. From the cooler 512 coolfluid is returned to the drive housing 412 and into the tank Mil throughthe swirl chamber.

A suitable underspeed switch 5M may be provided as shown in FIG. 21associated with governor 457 for the purpose of disconnecting thegenerator outputs from the other generators on the craft at apredetermined abnormal underspeed. An injector 515 is provided forpressurizing the drive and generator housing, and a charge relief valve516 ports excess charge fluid directly back to the reservoir or tank470. If desired, a charge pressure switch 517 may be provided for remoteindication of the charge pressure level.

' Iclaim:

l. A drive and generator combination, comprising: a generator having astationary stator and a rotor adapted to be driven at a substantiallyconstant speed, a constant speed drive for driving the rotor includingan input shaft member adapted to be driven by a prime mover, an outputshaft member connected to drive the rotor, differential gearing betweenthe input and output shaft members including a control gear for varyingthe speed of the output shaft member with respect to the input shaftmember; a first hydraulic unit drivingly connected to one of saidmembers, a second hydraulic unit ill drivingly connected to said controlgear, conduit means hydraulically interconnecting said first and secondhydraulic units, control means for varying the displacement of one ofsaid hydraulic units to maintain a substantially constant rotor speed,housing means for said generator, said differential and said hydraulicunits, means for delivering control fluid to said control means, meansfor delivering hydraulic fluid to said generator, and a common sump insaid housing means for both of said fluids.

2. A drive and generator combination as defined in claim 1, including asingle scavenge pump in said housing means for scavenging fluid fromsaid common sump.

3. A drive and generatorcombination as defined in claim ll, including asingle charge pump in said housing means for supplying said fluid tosaid control means and to said generator.

d. A drive and generator combination as defined in claim 3, includingmeans for supplying lubrication fluid to said differential, said chargepump being connected to supply said lubrication fluid to thedifferential.

5. A drive and generator combination as defined in claim 1, wherein saidmeans for supplying fluid to said generator includes means for supplyingcooling hydraulic fluid in direct contact with said stator.

6. A drive and generator combination as defined in claim 1, wherein saidmeans for supplying fluid to said generator includes means for supplyingcooling hydraulic fluid in direct contact with said rotor.

7. A drive and generator combination as defined in claim 1, wherein saidhousing means includes a reservoir hydraulically separate from said sumpand adapted to contain fluid to be supplied to both the drive and thegenerator, a single charge pump for receiving fluid from said reservoirand for conveying the fluid to the control means and said generator.

b. A drive and generator combination as defined in claim 7, including. ascavenge pump in said housing means for delivering fluid from saidcommon sump to said reservoir.

9. A drive and generator combination, comprising: a generator having astationary stator and a rotor adapted to be driven at a substantiallyconstant speed, a constant speed drive for driving the rotor includingan input shaft member adapted to be driven by a prime mover, an outputshaft member connected to drive the rotor, differential gearing betweenthe input and output shaft members including a control gear for varyingthe speed of the output shaft member with respect to the input shaftmember, a first hydraulic unit drivingly connected to one of saidmembers, a second hydraulic unit drivingly connected to said controlgear, conduit means hydraulically interconnecting said first and secondhydraulic units, control means for varying the displacement of one ofsaid hydraulic units to maintain a substantially constant rotor speed,said differential including a gear carrier in line with said input shaftmember and with said output member, said control gear being in line withsaid input shaft member and said output shaft member, said output shaftmember being directly connected to said rotor thereby eliminating thenecessity for drive gearing between the differential output member andthe rotor.

iii. A drive and generator combination as defined in claim 9, includinga third hydraulic unit drivingly connected to said one shaft member, afourth hydraulic unit drivingly connected to said control gear, secondconduit means interconnecting the third and fourth hydraulic units,second control means for varying the displacement of at least one ofsaid third and fourth hydraulic units, said first and second hydraulicunits being in back-to-back relation and offset with respect to the axisof said input and output shaft members, said third and fourth hydraulicunits being in back-to-back relation and offset with respect to saidinput and output shaft members.

ill. in an integrated constant speed drive and generator, thecombination, comprising: a generally cylindrical generator housing openat one end, a generally cylindrical drive housing open at one end, meansfor attaching the two housings in end ill to end relationship withtheapertured and open ends adjacent in one of the housings, a mechanicaldifferential including input gearing adapted to be driven by the inputshaft, output gearing adapted to drive the generator rotor, and controlgearing adapted to vary the speed ratio of the output gearing to theinput gearing, a hydrostatic transmission in the constant speed drivehousing including a pair of rotary axial piston hydraulic unitsconnected in closed hydraulic circuit, means for varying thedisplacement of at least one of the hydraulic units, means connectingone of the hydraulic units to be driven by the input shaft, and meansconnecting the other hydraulic unit to drive the control gearing in thedifferential, means responsive to the speed of the output gearing forcontrolling the displacement-varying means so that the output gearingand generator are driven at a constant speed regardless of variation inspeed of the input shaft, a reservoir in the constant speed drivehousing, a charge, pump communicating with the reservoir for supplyingcontrol fluid to the constant speed control, conduit means communicatingwith the charge pump for lubricating the differential gearing, conduitmeans communicating with the charge pump for cooling the generator,means for collecting leakage, lubricating and cooling fluid, and ascavenge pump in communication with the collecting means for deliveringfluid from the collecting means to the reservoir.

12. A drive and generator combination, comprising: a generator having astationary stator and a rotor adapted to be driven at a substantiallyconstant speed, a constant speed drive for driving the rotor includingan input shaft member adapted to be driven by a prime mover, an outputshaft member connected to drive the rotor, differential gearing betweenthe input and output shaft members including a control gear for varyingthe speed of the output shaft member with respect to the input shaftmember, a first hydraulic unit drivingly connected to one of saidmembers, a second hydraulic unit drivingly connected to said controlgear, conduit means hydraulically interconnecting said first and secondhydraulic units, control means for varying the displacement of one ofsaid hydraulic units to maintain a substantially constant rotor speed, acharge pump in said housing means for supplying control fluid to saidcontrol means, passage means in said housing means for supplying coolingfluid to said generator, said passage means being connected to receivecooling fluid from said charge pump, said passage means includingintegrally molded axial passage means in said housing means directlycommunicating with the generator stator.

13. A drive and generator combination, comprising: a generator having astationary stator and a rotor adapted to be driven at a substantiallyconstant speed, a constant speed drive for driving the rotor includingan input shaft member adapted to be driven by a prime mover, an outputshaft member connected to drive the rotor, differential gearing betweenthe input and output shaft members including a control gear for varyingthe speed of the output shaft member with respect to the input shaftmember, a first hydraulic unit drivingly connected to one of saidmembers, a second hydraulic unit.

drivingly connected to said control gear, conduit means hydraulicallyinterconnecting said first and second hydraulic units, control means forvarying the displacement of one of said hydraulic units to maintain asubstantially constant rotor speed, a charge pump in said housing meansfor supplying control fluid to said control means, passage means in saidhousing means for supplying cooling fluid to said generator, saidpassage means being connected to receive cooling fluid from said chargepump, and shaft means supporting said rotor, said passage meansincluding first passage means extending radially in said rotor shaftmeans and adapted to directly apply cooling fluid to said rotor.

14. A drive and generator combination, comprising: a generator having astationary stator and a rotor adapted to be driven at a substantiallyconstant speed, a constant speed drive for driving the rotor includingan input shaft member adapted to be driven by a prime mover, an outputshaft member connected to drive the rotor, differential gearing betweenthe input and output shaft members including a control gear for varyingthe speed of the output shaft member with respect to the input shaftmember, a first hydraulic unit drivingly connected to one of saidmembers, a second hydraulic unit drivingly connected to said controlgear, conduit means hydraulically interconnecting said first and secondhydraulic units, control means for varying the displacement of one ofsaid hydraulic units to maintain a substantially constant rotor speed, acharge pump in said housing means for supplying control fluid to saidcontrol means, passage means in said housing means for supplying coolingfluid to said generator, said passage means being connected to receivecooling fluid from said charge pump, and means freely communicating thegenerator and the differential and hydraulic units whereby theenvironment for the generator is the same as the environment for thedifferential and hydraulic units.

15. A drive and generator combination, comprising: a generator having astationary stator and a rotor adapted to be driven at-a substantiallyconstant speed, a constant speed drive for-driving the rotor includingan input shaft member adapted to be driven by a prime mover, an outputshaft member connected to drive the rotor, differential gearing betweenthe input and output shaft members including a control gear for varyingthe speed of the output shaft member with respect to the input shaftmember, a first hydraulic unit drivingly connected to one of saidmembers, a second hydraulic unit drivingly connected to said controlgear, conduit means hydraulically interconnecting said first and secondhydraulic units, control means for varying the displacement of one ofsaid hydraulic units to maintain a substantially constant rotor speed,housing means for said generator, said differential and said hydraulicunits, a rotor shaft carrying said generator rotor, said differentialincluding a first gear and a second gear in addition to said controlgear, at least two of said gears being located within said rotor shaft.t

16. A drive and generator combination as defined in claim 15, whereinsaid rotor shaft, said differential and said input shaft are aligned ona common axis.

17. A drive and generator combination as defined in claim 16, whereinsaid differential includes a first sleeve-shaped ring gear, a secondsleeve-shaped ring gear coaxial with said first ring gear, a carrierextending within said ring gears and having two interrneshing pinionsthereon, one of said sleeve ring gears being within said rotor shaft,one of said ring gears being stepped and having an external gearthereon, governor means for said control means, and gear means drivinglyinterconnecting said external gear and said governor means.

18. A drive and generator combination as defined in claim 15, saidhousing means having bearing means supporting one end of said rotorshaft, second bearing means in said housing means supporting the otherend of said rotor shaft, and third bearing means within said rotor shaftfor supporting one of said differential gears.

19. A drive and generator combination, comprising: a generator having astationary stator and a rotor adapted to be driven at a substantiallyconstant speed, a'constant speed drive for driving the rotor includingan input shaft member adapted to be driven by a prime mover, an outputshaft member connected to drive the rotor, differential gearing betweenthe input and output shaft members including a control gear for varyingthe speed of the output shaft member with respect to the input shaftmember, a first hydraulic unit drivingly connected to one of saidmembers, a second hydraulic unit drivingly connected to said controlgear, conduit means hydraulically interconnecting said first and secondhydraulic units, control means for varying the displacement of one ofsaid hydraulic units to maintain a substantially constant rotor speed, acharge pump for supplying cooling fluid to said generator rotor, firstpassage means in said generator rotor for 19, including third passagemeans in said differential for lubricating the same, said first passagemeans being connected to convey lubricating fluid to said third passagemeans.

3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,576,143 D t d April 27, 1971 Inventor(s) Stephen S. Baits It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

r- Column 11, line 71, after "extending", insert:

axially in said rotor shaft means and second passage means extending--Signed and sealed this 11th day of January 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. Attesting Officer ROBERT GO'ITSCHALK ActingCommissioner of Patents

1. A drive and generator combination, comprising: a generator having astationary stator and a rotor adapted to be driven at a substantiallyconstant speed, a constant speed drive for driving the rotor includingan input shaft member adapted to be driven by a prime mover, an outputshaft member connected to drive the rotor, differential gearing betweenthe input and output shaft members including a control gear for varyingthe speed of the output shaft member with respect to the input shaftmember, a first hydraulic unit drivingly connected to one of saidmembers, a second hydraulic unit drivingly connected to said controlgear, conduit means hydraulically interconnecting said first and secondhydraulic units, control means for varying the displacement of one ofsaid hydraulic units to maintain a substantially constant rotor speed,housing means for said generator, said differential and said hydraulicunits, means for delivering control fluid to said control means, meansfor delivering hydraulic fluid to said generator, and a common sump insaid housing means for both of said fluids.
 2. A drive and generatorcombination as defined in claim 1, including a single scavenge pump insaid housing means for scavenging fluid from said common sump.
 3. Adrive and generator combination as defined in claim 1, including asingle charge pump in said housing means for supplying said fluid tosaid control means and to said generator.
 4. A drive and generatorcombination as defined in claim 3, including means for supplyinglubrication fluid to said differential, said charge pump being connectedto supply said lubrication fluid to the differential.
 5. A drive andgenerator combination as defined in claim 1, wherein said means forsupplying fluid to said generator includes means for supplying coolinghydraulic fluid in direct contact with said stator.
 6. A drive andgenerator combination as defined in claim 1, wherein said means forsupplying fluid to said generator includes means for supplying coolinghydraulic fluid in direct contact with said rotor.
 7. A drive andgenerator combination as defined in claim 1, wherein said housing meansincludes a reservoir hydraulically separate from said sump and adaptedto contain fluid to be supplied to both the drive and the generator, asingle charge pump for receiving fluid from said reservoir and forconveying the fluid to the control means and said generator.
 8. A driveand generator combination as defined in claim 7, including a scavengepump in said housing means for delivering fluid from said common sump tosaid reservoir.
 9. A drive and generator combination, comprising: agenerator having a stationary stator and a rotor adapted to be driven ata substantially constant speed, a constant speed drive for driving therotor including an input shaft member adapted to be driven by a primemover, an output shaft member connected to drive the rotor, differentialgearing between the input and output shaft members including a controlgear for varying the speed of the output shaft member with respect tothe input shaft member, a first hydraulic unit drivingly connected toone of said members, a second hydraulic unit drivingly connected to saidcontrol gear, conduit means hydraulically interconnecting said first andsecond hydraulic units, control means for varying the displacement ofone of said hydraulic units to maintain a substantially constant rotorspeed, said differential including a gear carrier in line with saidinput shaft member and with said output member, said control gear beingin line with said input shaft member and said output shaft member, saidoutput shaft member being directly connected to said rotor therebyeliminating the necessity for drive gearing between the differentialoutput member and the rotor.
 10. A drive and generator combination asdefined in claim 9, including a third hydraulic unit drivingly connectedto said one shaft member, a fourth hydraulic unit drivingly connected tosaid control gear, second conduit means interconnecting the third andfourth hydraulic units, second control means for varying thedisplacement of at least one of said third and fourth hydraulic units,said first and second hydraulic units being in back-to-back relation andoffset with respect to the axis of said input and output shaft members,said third and fourth hydraulic units being in back-to-back relation andoffset with respect to said input and output shaft members.
 11. In anintegrated constant speed drive and generator, the combination,comprising: a generally cylindrical generator housing open at one end, agenerally cylindrical drive housing open at one end, means for attachingthe two housings in end to end relationship with the apertured and openends adjacent each other, a generator in the generator housing includinga stator stationarily mounted in the housing, and a rotor mounted forrotation within the stator, an input shaft mounted in one of thehousings, a mechanical differential including input gearing adapted tobe driven by the input shaft, output gearing adapted to drive thegenerator rotor, and control gearing adapted to vary the speed ratio ofthe output gearing to the input gearing, a hydrostatic transmission inthe constant speed drive housing including a pair of rotary axial pistonhydraulic units connected in closed hydraulic circuit, means for varyingthe displacement of at least one of the hydraulic units, meansconnecting one of the hydraulic units to be driven by the input shaft,and means connecting the other hydraulic unit to drive the controlgearing in the differential, means responsive to the speed of the outputgearing for controlling the displacement-varying means so that theoutput gearing and generator are driven at a constant speed regardlessof variation in speed of the input shaft, a reservoir in the constantspeed drive housing, a charge pump communicating with the reservoir forsupplying control fluid to the constant speed control, conduit meanscommunicating with the charge pump for lubricating the differentialgearing, conduit means communicating with the charge pump for coolingthe generator, means for collecting leakage, lubricating and coolingfluid, and a scavenge pump in communication with the collecting meansfor delivering fluid from the collecting means to the reservoir.
 12. Adrive and generaTor combination, comprising: a generator having astationary stator and a rotor adapted to be driven at a substantiallyconstant speed, a constant speed drive for driving the rotor includingan input shaft member adapted to be driven by a prime mover, an outputshaft member connected to drive the rotor, differential gearing betweenthe input and output shaft members including a control gear for varyingthe speed of the output shaft member with respect to the input shaftmember, a first hydraulic unit drivingly connected to one of saidmembers, a second hydraulic unit drivingly connected to said controlgear, conduit means hydraulically interconnecting said first and secondhydraulic units, control means for varying the displacement of one ofsaid hydraulic units to maintain a substantially constant rotor speed, acharge pump in said housing means for supplying control fluid to saidcontrol means, passage means in said housing means for supplying coolingfluid to said generator, said passage means being connected to receivecooling fluid from said charge pump, said passage means includingintegrally molded axial passage means in said housing means directlycommunicating with the generator stator.
 13. A drive and generatorcombination, comprising: a generator having a stationary stator and arotor adapted to be driven at a substantially constant speed, a constantspeed drive for driving the rotor including an input shaft memberadapted to be driven by a prime mover, an output shaft member connectedto drive the rotor, differential gearing between the input and outputshaft members including a control gear for varying the speed of theoutput shaft member with respect to the input shaft member, a firsthydraulic unit drivingly connected to one of said members, a secondhydraulic unit drivingly connected to said control gear, conduit meanshydraulically interconnecting said first and second hydraulic units,control means for varying the displacement of one of said hydraulicunits to maintain a substantially constant rotor speed, a charge pump insaid housing means for supplying control fluid to said control means,passage means in said housing means for supplying cooling fluid to saidgenerator, said passage means being connected to receive cooling fluidfrom said charge pump, and shaft means supporting said rotor, saidpassage means including first passage means extending radially in saidrotor shaft means and adapted to directly apply cooling fluid to saidrotor.
 14. A drive and generator combination, comprising: a generatorhaving a stationary stator and a rotor adapted to be driven at asubstantially constant speed, a constant speed drive for driving therotor including an input shaft member adapted to be driven by a primemover, an output shaft member connected to drive the rotor, differentialgearing between the input and output shaft members including a controlgear for varying the speed of the output shaft member with respect tothe input shaft member, a first hydraulic unit drivingly connected toone of said members, a second hydraulic unit drivingly connected to saidcontrol gear, conduit means hydraulically interconnecting said first andsecond hydraulic units, control means for varying the displacement ofone of said hydraulic units to maintain a substantially constant rotorspeed, a charge pump in said housing means for supplying control fluidto said control means, passage means in said housing means for supplyingcooling fluid to said generator, said passage means being connected toreceive cooling fluid from said charge pump, and means freelycommunicating the generator and the differential and hydraulic unitswhereby the environment for the generator is the same as the environmentfor the differential and hydraulic units.
 15. A drive and generatorcombination, comprising: a generator having a stationary stator and arotor adapted to be driven at a substantially constant speed, a constantspeed drive for driving the rotor including an input shaft memberaDapted to be driven by a prime mover, an output shaft member connectedto drive the rotor, differential gearing between the input and outputshaft members including a control gear for varying the speed of theoutput shaft member with respect to the input shaft member, a firsthydraulic unit drivingly connected to one of said members, a secondhydraulic unit drivingly connected to said control gear, conduit meanshydraulically interconnecting said first and second hydraulic units,control means for varying the displacement of one of said hydraulicunits to maintain a substantially constant rotor speed, housing meansfor said generator, said differential and said hydraulic units, a rotorshaft carrying said generator rotor, said differential including a firstgear and a second gear in addition to said control gear, at least two ofsaid gears being located within said rotor shaft.
 16. A drive andgenerator combination as defined in claim 15, wherein said rotor shaft,said differential and said input shaft are aligned on a common axis. 17.A drive and generator combination as defined in claim 16, wherein saiddifferential includes a first sleeve-shaped ring gear, a secondsleeve-shaped ring gear coaxial with said first ring gear, a carrierextending within said ring gears and having two intermeshing pinionsthereon, one of said sleeve ring gears being within said rotor shaft,one of said ring gears being stepped and having an external gearthereon, governor means for said control means, and gear means drivinglyinterconnecting said external gear and said governor means.
 18. A driveand generator combination as defined in claim 15, said housing meanshaving bearing means supporting one end of said rotor shaft, secondbearing means in said housing means supporting the other end of saidrotor shaft, and third bearing means within said rotor shaft forsupporting one of said differential gears.
 19. A drive and generatorcombination, comprising: a generator having a stationary stator and arotor adapted to be driven at a substantially constant speed, a constantspeed drive for driving the rotor including an input shaft memberadapted to be driven by a prime mover, an output shaft member connectedto drive the rotor, differential gearing between the input and outputshaft members including a control gear for varying the speed of theoutput shaft member with respect to the input shaft member, a firsthydraulic unit drivingly connected to one of said members, a secondhydraulic unit drivingly connected to said control gear, conduit meanshydraulically interconnecting said first and second hydraulic units,control means for varying the displacement of one of said hydraulicunits to maintain a substantially constant rotor speed, a charge pumpfor supplying cooling fluid to said generator rotor, first passage meansin said generator rotor for carrying cooling fluid in a direction towardthe differential and second passage means for carrying cooling fluidfrom said charge pump to said first passage means.
 20. A drive andgenerator combination as defined in claim 19, including third passagemeans in said differential for lubricating the same, said first passagemeans being connected to convey lubricating fluid to said third passagemeans.